I installed OpenWrt to my Ubnt Rocket M5 router, but it has a but that resets all the configurations after reboot. Later I knew Ubnt updated the u-boot and changed rootfs size from 6528k to 5760k, since the XW 5.6.x version.
So I want to reinstall the stock firmware by the TFTP method. The device only accepts firmware version >= 5.6.x, and the TFTP process seems normal. But the device just does not boot, stucking at
Booting Atheros AR934x
setenv mtdparts 'mtdparts=ath-nor0:256k(u-boot),64k(u-boot-env),1024k(kernel),6528k(rootfs),256k(cfg),64k(EEPROM)'
This make the device boot normally, and I can finally access to the 192.168.1.20 webpage. But this change is NOT PERSISTENT. Everytime after reboot, rootfs size changes back to 5760k, making the device can not boot again.
I also tried to upload a firmware via 192.168.1.20 webpage, but it just says "Firmware check failed" with error code -109.
So any ideas about what's wrong and what can I do?